Methyl-2-(dimethylamino)-N-[[methylaminocarbonyl]oxy]-2-oxo-ethanimidothioa te, hereafter referred to by the common name oxamyl, is extremely effective as a contact type, broad spectrum insecticide and nematicide. It is especially useful in pre-plant soil incorporation treatment.
The long-term insecticidal and nematicidal performance of oxamyl is impaired by its disappearance in soil, a problem believed to be accelerated by rainfall, aeration, sunlight, alkalinity and elevated temperatures. This instability was discussed by J. Harvey, Jr. and J. C-Y Hau, Agricultural and Food Chemistry, Vol. 26, No. 3, page 536 (1978). Also, water leachability is a major problem, especially in sandy soils, due to the high solubility of oxamyl in water, about 20% at 25.degree. C. Thus, in heavy rainfall, oxamyl could be diluted to a sub-effective level for nematodes or simply be washed away. Another problem relating to oxamyl use is the handling safety of oxamyl as it has high toxicity, exemplified by an LD.sub.50 rating of of 5.4 mg/kg.
These problems could conceivably be eliminated or at least reduced by providing an effective barrier for an oxamyl formulation. Such a barrier should strike the critical balance between gradually releasing sufficient oxamyl to control nematodes while at the same time holding in reserve oxamyl that would be lost to the environment due to factors cited above.
It is known to use slow-release systems for applying insecticides. One problem with such systems, however, is that they normally exhibit reduced early activity. This is due to the presence of the barrier material which reduces the availability of the insecticide.
There thus exists a need for prolonging the excellent insecticidal and nematicidal activity of oxamyl without impairing its initial activity. There is also a need for improving the handling safety of oxamyl.